Process for making a nonwoven web derived from lactic acid, web produced thereby, and apparatus therefor

Abstract

The invention relates to a process for the manufacture of a nonwoven web using filaments of melted polymers, of the type including the steps of spinning the polymer or polymers, of cooling, drawing and laying down fibers on a belt and of bonding said fibers by calendering in order to form said nonwoven web (15), which process furthermore includes a treatment (13, 14) of setting/adjusting the degree of crystallinity of and the internal tension in the fibers making up the nonwoven web. The invention also relates to the nonwovens obtained by the process and to the installations for implementing it.

We claim: 
     
       1. A process for the manufacture of a nonwoven web using fibers of one or more melted polymers, consisting of lactic acid or a derivative thereof, and wherein the process comprises the steps of spinning the melted polymer to form the fibers, cooling, drawing and laying down the fibers on a belt, bonding said fibers by calendaring to form the web, and setting/adjusting the degree of crystallinity of and the internal tension in the fibers of the nonwoven web, the setting/adjusting consisting essentially of biaxial setting after the calendaring, then low temperature heating the web under biaxial tension, followed by cooling. 
     
     
       2. The process of claim 1, wherein the heating is oven heating for 10 to 60 s at a temperature varying from 80° C. to 150° C. 
     
     
       3. The process of claim 1, wherein the heating is heating for a few seconds by infrared radiation at a temperature varying from 80° C. to 150° C. 
     
     
       4. The process of claim 1 wherein the polymer is a polymer of L-lactic acid or D-lactic acid. 
     
     
       5. The process of claim 4 wherein the polymer is a polymer of L-lactic acid and D-lactic acid. 
     
     
       6. The process of claim 1 wherein the degree of crystallinity is increased. 
     
     
       7. The process of claim 1 wherein the internal tension in the fibers is relaxed. 
     
     
       8. The process of claim 1 wherein the degree of crystallinity is increased and the internal tension in the fibers is relaxed. 
     
     
       9. An apparatus for implementing the process of claim 1 for the manufacture of a non-woven web using polymers, of the type including means of spinning the polymer or polymers, of cooling, drawing and laying down fibers on a belt and of bonding said fibers by calendaring in order to form a web, which apparatus furthermore includes treatment means for setting/adjusting the degree of crystallinity of and the internal tension in fibers making up the web, wherein the setting/adjusting treatment means comprises means for biaxial-setting the web and means for low-temperature heating of the web under biaxial tension. 
     
     
       10. The apparatus of claim 9, wherein the setting/adjusting treatment means consist of biaxial-setting means and of heating means selected from the group: oven, and infrared radiation. 
     
     
       11. The apparatus of claim 9, wherein the setting/adjusting treatment means further comprises cooling means for cooling the web following the means for low temperature heating.